Drill and method of manufacturing machined product

Abstract

A drill may include a body extending from a first end toward a second end, and the body may include an outer peripheral surface and a cutting edge. The cutting edge may include a first cutting edge and a second cutting edge. The second cutting edge may be positioned closer to the second end and the outer peripheral surface than the first cutting edge. The second cutting edge may include a first part, a second part and a third part. The second part may be positioned closer to the outer peripheral surface than the first part and may be positioned closer to the second end as close to the first part. The third part may be positioned closer to the first cutting edge than the first part and may be positioned closer to the second end as close to the first part.

The invention claimed is: 
     
       1. A drill, comprising:
 a body having a rod-shape and extending along a rotation axis from a first end toward a second end, wherein 
 the body comprises:
 an outer peripheral surface; 
 a cutting edge positioned on a side of the first end; and 
 a flute extending from the cutting edge toward the second end, 
 
 the cutting edge comprises:
 a first cutting edge extending from a side of the rotation axis toward the outer peripheral surface; and 
 a second cutting edge positioned closer to the second end and the outer peripheral surface than the first cutting edge, 
 
 an end portion of the first cutting edge on a side of the outer peripheral surface is positioned closer to the second end than an end portion of the first cutting edge on the side of the rotation axis, 
 the second cutting edge comprises:
 a first part positioned closest to the second end; 
 a second part connected to the first part, the second part is positioned closer to the outer peripheral surface than the first part, and positioned closer to the second end as close to the first part; and 
 a third part connected to the first part, the third part is positioned closer to the first cutting edge than the first part, and the third part is positioned closer to the second end as close to the first part, and 
 
 the first part has a concave shape recessed toward the second end in a side view, 
 the body further comprises a peripheral cutting edge that is positioned at least at a portion of a ridge line at which the outer peripheral surface and the flute intersect and that is connected to the cutting edge, 
 the cutting edge further comprises a fourth cutting edge connected to the peripheral cutting edge, 
 the fourth cutting edge comprises: a third portion; and a fourth portion positioned closer to the outer peripheral surface than the third portion, and 
 a radius of curvature of the third portion is smaller than a radius of curvature of the fourth portion. 
 
     
     
       2. The drill according to  claim 1 , wherein the second part is linear. 
     
     
       3. The drill according to  claim 1 , wherein
 the cutting edge further comprises a third cutting edge connected to the first cutting edge and the third part and having a convex shape in the side view. 
 
     
     
       4. The drill according to  claim 1 , wherein
 in the side view,
 the first cutting edge is linear, 
 a line obtained by extending the first cutting edge toward the outer peripheral surface is defined as a first virtual extended line, and 
 the fourth cutting edge is positioned closer to the second end than the first virtual extended line. 
 
 
     
     
       5. The drill according to  claim 1 , wherein the fourth cutting edge has a convex curved shape in the side view. 
     
     
       6. The drill according to  claim 1 , wherein
 the cutting edge comprises a fifth cutting edge that is located between the second cutting edge and the outer peripheral surface and that is linear. 
 
     
     
       7. The drill according to  claim 6 , wherein
 in the side view, 
 the first cutting edge is linear, 
 a line obtained by extending the first cutting edge toward the outer peripheral surface is defined as a first virtual extended line, and 
 an end portion of the fifth cutting edge on the side of the outer peripheral surface is positioned closer to the side of the first end than the first virtual extended line. 
 
     
     
       8. The drill according to  claim 6 , wherein
 in a front view of the first end, 
 the first cutting edge is linear, 
 a line obtained by extending the first cutting edge toward the outer peripheral surface is defined as a second virtual extended line, and 
 the fifth cutting edge is away from the second virtual extended line. 
 
     
     
       9. The drill according to  claim 8 , wherein
 the fifth cutting edge is positioned rearward of the second virtual extended line in a rotating direction in the front view of the first end. 
 
     
     
       10. The drill according to  claim 6 , wherein
 the cutting edge comprises a sixth cutting edge connected to the second part and the fifth cutting edge. 
 
     
     
       11. The drill according to  claim 6 , wherein
 the cutting edge further comprises a fourth cutting edge connected to the peripheral cutting edge, and 
 the fourth cutting edge is connected to the fifth cutting edge and the peripheral cutting edge. 
 
     
     
       12. The drill according to  claim 1 , wherein the third part has a concave curved shape in the side view. 
     
     
       13. The drill according to  claim 1 , wherein
 the flute comprises:
 a first surface extending from the first part toward the second end; and 
 a second surface extending from the second part toward the second end, and 
 an axial rake angle on the second surface is smaller than an axial rake angle on the first surface. 
 
 
     
     
       14. The drill according to  claim 1 , wherein
 in a front view of the first end, 
 the body comprises a concave groove portion extending rearward in the rotating direction from the second cutting edge. 
 
     
     
       15. The drill according to  claim 1 , wherein
 the third part comprises: a first portion; and a second portion positioned closer to the outer peripheral surface than the first portion, and 
 a radius of curvature of the first portion is larger than a radius of curvature of the second portion. 
 
     
     
       16. A method of manufacturing a machined product, comprising the steps of:
 rotating the drill according to  claim 1 ; 
 bringing the drill that is rotating into contact with a workpiece; and 
 separating the drill from the workpiece. 
 
     
     
       17. A drill, comprising:
 a body having a rod-shape and extending along a rotation axis from a first end toward a second end, wherein 
 the body comprises:
 an outer peripheral surface; 
 a cutting edge positioned on a side of the first end; and 
 a flute extending from the cutting edge toward the second end, 
 
 the cutting edge comprises:
 a first cutting edge extending from a side of the rotation axis toward the outer peripheral surface and being closer to the second end at an end closer to the outer peripheral surface; and 
 a second cutting edge positioned closer to the second end and the outer peripheral surface than the first cutting edge and having a concave shape that is recessed toward the second end, 
 
 the second cutting edge comprises a first part comprising a portion positioned closest to the second end; 
 the first part has a concave curved shape recessed toward the second end in a side view, 
 the body further comprises a peripheral cutting edge that is positioned at least at a portion of a ridge line at which the outer peripheral surface and the flute intersect and that is connected to the cutting edge, 
 the cutting edge further comprises a third cutting edge connected to the first cutting edge and the third part and having a convex shape in the side view and a fourth cutting edge connected to the peripheral cutting edge, 
 the fourth cutting edge comprises: a third portion; and a fourth portion positioned closer to the outer peripheral surface than the third portion, and 
 a radius of curvature of the third portion is smaller than a radius of curvature of the fourth portion. 
 
     
     
       18. The drill according to  claim 17 , wherein
 the cutting edge comprises a fifth cutting edge that is located between the second cutting edge and the outer peripheral surface and that is linear. 
 
     
     
       19. The drill according to  claim 18 , wherein
 the first cutting edge is linear, 
 a line obtained by extending the first cutting edge toward the outer peripheral surface is defined as a second virtual extended line, and 
 the fifth cutting edge is away from the second virtual extended line in a front view of the first end. 
 
     
     
       20. The drill according to  claim 19 , wherein
 the fifth cutting edge is positioned rearward of the second virtual extended line in a rotating direction in the front view of the first end. 
 
     
     
       21. A drill, comprising:
 a body having a rod-shape and extending along a rotation axis from a first end toward a second end, wherein 
 the body comprises:
 an outer peripheral surface; 
 a cutting edge positioned on a side of the first end; and 
 a flute extending from the cutting edge toward the second end, 
 
 the cutting edge comprises:
 a first cutting edge extending from a side of the rotation axis toward the outer peripheral surface; and 
 a second cutting edge positioned closer to the second end and the outer peripheral surface than the first cutting edge, 
 
 an end portion of the first cutting edge on a side of the outer peripheral surface is positioned closer to the second end than an end portion of the first cutting edge on the side of the rotation axis, 
 the second cutting edge comprises:
 a first part positioned closest to the second end; 
 a second part connected to the first part, positioned closer to the outer peripheral surface than the first part, and positioned closer to the second end as close to the first part; and 
 a third part connected to the first part, positioned closer to the first cutting edge than the first part, and positioned closer to the second end as close to the first part, and 
 
 the first part has a concave curved shape recessed toward the second end in a side view, 
 the third part comprises: a first portion; and a second portion positioned closer to the outer peripheral surface than the first portion, and 
 a radius of curvature of the first portion is larger than a radius of curvature of the second portion.